Many species of beetle produce large horns that are used as weapons or shields. The resources required to build these horns, though, might be diverted from other useful structures. To test this, Emlen (2001) measured the sizes of wings and horns in 19 females of the beetle species Onthophagus sagittarius. Both traits were scaled for body-size differences and hence are referred to as relative horn and wing sizes. Emlen’s data are shown in the following scatter plot along with the least squares regression line (Y=−0.13−132.6X).

a. Use these results to calculate the residuals.

b. Use your results from part (a) to produce a residual plot.

c. Use the graph provided and your residual plot to evaluate the main assumptions of linear regression.

d. In light of your conclusions in part (c), what steps should be taken?

Transcribed Image Text:

Relative wing mass (µg) 30- 20 10 0- -10- -20- -30 -40 -0.15 -0.10 -0.05 0.00 0.05 0.10 Relative horn size (mm²)